Section 4 The construct of bilingual proficiency
There is still little consensus among researchers as to the nature of language proficiency. For example, a model proposed by HernandezChavez, Burt and Dulay (1978) comprised sixty-four separate pro ficiencies, each of which, hypothetically, is independently measurable. At the other extreme is Oiler’s (1978, 1979) claim that ‘there exists a global language proficiency factor which accounts for the bulk of the reliable variance in a wide variety of language proficiency measures’ (1978, p. 413). This factor is strongly related to cognitive ability and academic achievement measures and is about equally well measured by certain types of listening, speaking, reading and writing tasks.